Pivoted armature electromagnetic switch



24, 1965 v. G. MATHISON ETAL 3,202,782

PIVOTED ARMATURE ELECTROMAGNETIC SWITCH Filed Dec. 26, 1961 2 Sheets-Sheet 1 W/LBUQ 7. #QQD/SOA/ INVENTORS Aug. 24, 1965 v. G. MATHISON ETAL 3,202,782

PIVOTED ARMATURE ELECTROMAGNETIC SWITCH Filed Dec. 26. 1961 2 Sheets-Sheet 2 762 1Q @C 100702 6; 4147/4/50 w/aeae Z'A/fiQfl/SU/V i INVENTORS United States Patent Victor G. Mathison and Wilbur T. Hardison, Riverside,

Califl, assignors to Bourns, Inc. Filed Dec. 26, 1961, Ser. No. 161,959 6 Claims. (CL 200-87) The presently disclosed invention pertains to electromagnetic switches, that is, electromagnetically operated switches, of the type commonly termed relays; and more specifically to extremely small electromagnetic switches or relays having extreme resistance to malfunctioning under exceptionally adverse environmental influences such as vibration and/ or acceleration, very high and/or very low temperature, high humidity, etc., while contemporaneously possessing the very desirable attributes of very low operating-power requirements, extremely small size and low weight, simplicity of construction and assembly, and marked durability. As herein used, the term very small is employed to designate a relay or electromagnetically operated switch device the maximum cross-sectional dimension of which is of the order of three-fours of an inch or less.

The advent of What is in the vernacular termed the space age, and the attendant'increased activity in aerial and orbital vehicles and the like, has produced a demand for electrical, mechanical, electro-mechanical, chemical, and other apparatuses, characterized by minimum weight and spatial dimensions, extreme reliability under exceptionally severe adverse environmental operating conditions, and superior longevity. That pressing demand has induced the development of what have been termed miniature and subminiature components and devices of many kinds for use in vehicles of the noted types. That miniaturization, so-called, of what in general land and marine applications of components are relatively large and sometimes complex devices, involves considerably more than mere scalar reduction of size of conventional devices; since in many instances as the sizes of conventional parts of devices are reduced the parts become too slender, or too thin, or otherwise incompetent, to perform their intended functions. Further, in a scalar reduction of size, a situation'is arrived at in which assembly operations cannot be satisfactorily accomplished with retention of ability to mass-produce the devices with an acceptable degree of uniformity. Additionally, it is found that in some instances, heat-transferring ability, magnetic-circuit susceptibility, and like essential characteristics, are adversely aifected by proportionate sizereduction. The mentioned facts preclude, in a large majority of instances, the production of an operable miniature replica of an ordinary normal-size commercial instrument or device; and force into use such practices as making a single part perform a plurality of functions previously performed by respective individual parts, utilization of a plurality of characteristics of the material of which a part is made, and the like. The mentioned factors and facts are involved, and the practices mentioned are used, in the present invention which is characterized by marked success in meeting specifications calling for extensive reduction in physical size and weight while providing considerable improvement in operating characteristics, longevity, and immunity to extremes of adverse environment.

The electromagnetic switch of the invention is an hermetically-sealed unit, enclosed in a housing or container one end of which serves as a base or foundation for the operating parts and which end includes glass-to-metal seal means with provisions for electrically insulated terminals. The container-end, or foundation, and hereinafter termed a header, serves to rigidly support a plurallimbed preferably non-magnetic table-like frame or pedestal which in the illustrated embodiment comprises four depending legs and a pair of laterally disposed limbs or arms to which depending magnetic poles of the U- shaped core of an electromagnet are fusion-united so that the electromagnet is fixedly secured to and supported by the frame or pedestal. The core of the electromagnet is a single unitary piece of magnet iron, on the middle portion of which is molded a spool or bobbin of insulation having excellent physical properties. By that construction the relatively heavy fixed parts of the device are in effect integrally united into a unitary rigid structure that is exceptionally resistant to deterioration under the influence of vibration or shock and/ or high temperature. Other physical characteristics of the fixed structure are hereinafter stated in detail. The pedestal supports in dependin relation between its legs a spindle or pivot-pin, upon which is rotatably mounted a dynamically-balanced armature for cooperation with the opposed contiguous poles of the electromagnet. The ends of the armature are constrained to to and fro rotary movements between respective electromagnet poles and suitable stop means, and one end is urged toward the stop means by a spring means whose effect is overcome when the electromagnet is energized. Thus the armature is constructed and arranged for movement between first and second positions or attitudes corresponding, respectively, to the de-energized and to energize states of the electromagnet. Afiixed to the armature and depending therefrom is a contact-actuator formed as a stiff resilient rod or wire provided with an insulative knob or head at its lower end, the arrangement being such that as the armature moves from first to second positions the bead is similarly moved. The head serves when so removed to stress a resilient reed-like electric contact device from a first position to a second position in which contact is made with a stationary contact member, to close an electric circuit. Tne stationary contact member, and a stop or optional second contact member, as well as a supporting pin for the read like flexible contact device, are suitably supported in proper but adjustable juxtaposition by the header. The header has sealed thereto around its periphery the lower edge of a fluid-tight can-like cover which with the header forms the aforementioned housing. By forming the armature as a dynamically balanced section of a ferromagnetic extrusion, it is made efiicient and effective as an element of the magnetic circuit while concurrently being mexpensive and immune to malfunctioning induced by vibration,

acceleration, shock, etc. By forming the electromagnet core as a single piece of magnetic material, the core is made magnetically efiicient, structurally strong for supporting the electromagnet coil, and, more importantly, permits molding in situ thereon the bobbin or spool for containing the coil of the magnet. By thus molding the made suitable for use in very hot ambients without danger of failure. By securing the legs or poles of the electromagnet to the wings of the pedestal by fusion, e.g., by welding, and by uniting the legs of the pedestal to the header by fusion, all of the principal stationary components of the device are in elfect united into a single unitary Another object is to provide, for an electromagnetic switch, a substantially integrally-united structure comprising a magnetic core, a coil-bobbin, and a core-supporting device. 7 7

Another object of the invention is to provide an electrornagnetic switch having increased immunity to adverse efi ects caused by vibration and high ambient temperature.

Another object of the invention is to provide a reliable electromagnetic switch of very small weight and dimen- SIOIIS.

Another object of the invention is to provide a rigid integral structure comprising a magnetic core having first and second spaced-apart poles and a non-magnetic supporting device bridging the poles and fusion united thereto, to provide an integral structure having no gap in the magnetic circuit of the core.

Another object is to provide for a very small electromagnetic switch, a single-piece U-shaped core having spaced-apart first and second poles and a coil-bobbin integrally molded on the core.

Other objects and advantages of the invention will hereinafter be made apparent in the appended claims and the description of a preferred physical embodiment of the invention as illustrativcly depicted in the accompanying drawings, in which drawings:

FIGURE 1 is an isometric view of an hermeticallysealed electromagnetic switch unit or device according to the invention, shown substantially at full scale;

FIGURE 2 is a view of three principal component units or sub-assemblies comprised in the exemplary switch unit depicted in FIG. 1, in dis-assembled array,

and considerably enlarged, with a portion of a coil covering removed;

FIGURE 3 is a face view of the switch unit depicted in FIG. 1, with the can or cover of the container removed and with the parts grossly enlarged to facilitate illustration;

FIGURE 4 is a sectional view taken as indicated by line 4-4 in FIG. 3; V I FIGURE 5 is a sectional view taken as indicated by line 5-5 in FIG. 3;.

FIGURE 6 is a partial sectional view taken on a plane through the device, parallel to the magnet core, with the cover or can removed;

FIGURE 7 is an end view of the device with the can -or cover removed, viewed in the direction indicated by the arrow inVFIG. 6; 7

FIGURE 8 is a top view of the magnet-core and integrally-molded coil-bobbin and coil, with a portion of the coil broken away to show details;

FIGURE 9 is a View in section of a fragmentary portion of the fusion-united unit comprising a frame-or-pedestal wing and a magnetic core; 7 FIGURE 10 is a view of an electromagnet armature unit or device as a whole is denoted by ordinal 10. The

unit comprises a housing including a can-like cover 12 in,

which operating parts of .the unit are disposed for protection and isolation from foreign material, and for immersion in an inert-gas atmosphere. Referring to FIG. 2, a v

base or header 14, which upon completion of assembly of the device is sealed around its periphery to the lower rim edge of cover 12 by soldering or like means and procedure, is arranged to support a set 16 of electrical terminals or leads 16a, 16b, 16c, 16d and Me which are mounted in an insulative insert Mi that is fusion-united to the metallic rim or block 1411 of the header by conventional glass-to-metal sealing methods. Also supported by header 14 is a non-magnetic frame or pedestal 118 whose depending legs 18p, ISq, 18r, 18s are provided with positioning notches such as those indicated at 19 in FIG. 2 and are adapted for close mating with respective grooves (such as those at 14g) formed or provided in the sides of header 14. As is indicated in FIGS. 2 and 3, the lower or foot portion of each of the depending limbs or legs of the frame is readily slipped into accurately determined position in a respective one of the grooves in header 14 and is there spot welded or fusionunited with the rim or block of the header. Thus the frame or pedestal is securely and accurately united with the header to form an integral subassembly unit.

The frame or pedestal 18 (FIG. 2) is provided with first and second oppositely extending arms or limbs 18m, 1812, which are formed as integral parts of the stamping composing the pedestal. ArrnslSm and 18a are arranged to serve as means for supporting an electromagnet on the pedestal and for permitting integration of the electromagnet with the pedestal and header to form a single integral unit of relatively fixed components comprising those'three principal subassemblies. Accordingly, and as previously noted, the pedestal is non-magnetic and may be of nickel-silver. The electromagnet 20, illustrated as a detached subassembly in FIG. 2 and shown in FIG. 8 with portions broken away, comprises essentially a U- shaped single-piece magnetic core 260, an insulative coilretaining spool or bobbin 2% molded in situ on the core, and a coil or Winding 20w of insulated alloy wire of high conductivity. The core, (FIG. 11) is preferably coined from magnet iron, and comprises first and second depending limbs or legs 20m, Ziin of rectangular cross-section,

and a body portion 200 of circular cross-section integral with and interconnecting thelegs. The insulative bobbin, Ztlb (FIGS. ,2 and 6), may assume a variety of suitable physical configurations all of which include a central cylindrical portion 219;; (FIG. 8) encircling the core body .200 and end discs or flanges 2011., 29 The end discs or flanges are provided with apertures or slots suchas 20v as shown, through which the end portions 20w of the wire of the winding Zfiw are drawn at the commencement and termination of the coil-winding operation. The bobbin is formed of an insulative polyfiu'orocarbon resin of characteristics permitting operation of the magnet in highof the unitary magnet-core 200 are fusion-united (as by spot welding or'the like), to respective ones of the aforementioned arms idm, 1811 of the pedestal 18, as indicated at 23 in FIGS. 4 and 9. Thus the coil bobbin Zttb, the magnet core 200, the pedestal 18, and the housing base or header 14 are all firmly united into an integral structure the component portions of which are thus positively prevented from relative displacement incident to vibration or physical shock that may be'experienced by the device in service. The winding or coil is wound onto the core and spool prior to attachmentof the legs of the core to the pedestal; and by suitable application of self-curing; 'resin during and/or subsequent to winding of the wire,

the coil itself may be integrally united with. the bobbin,

whereby relative displacement of the wire and bobbin is effectively precluded. By the aforedescribed means the principal stationary components of the electromagnetic switch device are integrated into a unitary structure between the component sub-assernblies of which relative motion is thus precluded. Thus durability, reliability, and longevity are greatly increased over those in switches -in which some measure of relative motion between stationary components is permitted.

Secured to an extension of terminal 16a (FIG. 2) is the fixed end of a resilient reed-like elastic contact device 16a. The elastic contact device may be made of suitable material such as beryllium-copper, and preferably is gold-plated. The elastic contact device 16a may be a simple resilient reed as illustrated, plated as indicated; or it may comprise at the active contact zone an insert or plating of contact-alloy such as palladium-silver or the like. Secured to terminals 16d and 16s are respective deformable but stationary or fixed contact members 16d and 16s, each being fusion-united to its corresponding terminal and being disposed for engagement by a respective side of the elastic contact device 16a. The arrangement is such that the elastic contact device 16a is normally stressed into contact with contact member 16e' and thus is positioned with its free end spaced away from contact member 16d. That arrangement and disposition of the contact means is illustrated in FIG. 7. The contact members 16d and 162 are coined or stamped from suitable sheet metal or alloy, and preferably are gold plated. Each is fusion-united to a respective one of the terminals 16d and 162 as indicated, and is positionally adjusted by deformation in a known manner.

Firmly secured to pedestal 18 as by fusion or, as indi cated in FIG. 6, by being mounted in an aperture in the platform of the pedestal and peened or swaged, is an armature-supporting pivot or pin 18:. The pin, formed as indicated in the drawings, is thus very precisely positioned and in effect integrally united with the pedestal. The pin thus has a cylindrical bearing portion suspended below the platform of the pedestal, and' a head portion serving to aid in firmly securing the pin to the platform and in spacing the presently described armature away from the platform. Rotatably mounted on pin 18t is,a dynamically balanced ferromagnetic armature 22 (FIGS. 4

and of special configuration and of integral one-piece construction. As is evident from the drawings, the armature is dual-limbed and is provided with a central bore 22b through which pin 181 extends. The armature is retained on the pin by means of an E retainer ring 24 which is seated in a complementary circumferential groove formed on the lower end of the pin, as indicated in FIG. 6. Upper and lower anti-friction washers 25, 25, may be utilized as shown, and a small amount of molybdenum disulphide or other suitable lubricant may be used be tween the armature and the pin to reduce to a minimum the effects of friction. The armature is thus constructed and arranged for easy albeit precise rotary movements on the pin. As is clearly indicated in FIGS. 4 and 10, the double-ended armature has its opposite or first and second limbs or arms, 22m, 2211, each offset at a respective .side of the median plane of the frame, and arranged to cooperate with a respective one of the depending limbs of the electromagnet core. The two offset ends of the armature are integral with the body portion 221 which includes a hub-like portion 22h that is pierced by the bore. By thus offsetting the limbs of the armature, the

electromagnet core may be formed with the axes of the integral part of pedestal T8. The armature, in the deenergized state of the electromagnet, is urged into contact with the stop 18x by a compression spring 26 that is supported between opposed tits formed on the pedestal and on one limb or arm of the armature. When the electromagnet is energized, the armature is attracted by the magnetized poles of the magnet, and the effect of the spring 26 is overcome and the arms of the armature are drawn into contact with the poles of the magnet. While a compression spring is shown, other equivalent means of biasing the armature may be employed. The poles of the magnet serve, as is indicated in FIG. 4, as stops for limiting motion of the armature in the other (clockwise, as shown) direction. A small extent of the last part of the motion of the armature incident to energization of the magnet is used to operate contact means of the switch presently to be described.

In the very small electromagnetically operated switches or relays of the prior art, it was necessary to provide upstanding fianges or horns above the platform of the frame, to support and hold the magnet coil in place. The flanges or horns had apertures through which respective L-shaped half-sections of a two-piece magnet core were inserted into the bore of the coil. The depending limbs of the two-piece core were suitably secured to the frame. That construction required that the coil be wound separately from the core, and that a magnetically-inordicient two-piece core be used. Thus the prior art structures not only were characterized by an inefficient magnetic circuit, but also permitted relative movements between the two pieces of the core and thus allowed changes in the already inefhcient magnetic circuit and hence undesirable changes with time in the electromagnetic characteristics of a specific relay, and lack. of unifromity among relays of a group. Further, that construction was characterized by weakness in the rigidity of the structure comprising the magnet and frame, due to single-point attachment of core members to the frame. The present invention,utilizing an integral one-piece magnet core, prevents variation with time of the magnetic reluctance of the core between poles and makes possible the desired uniformity of all relays of a group, prevents vibration between parts of a two-piece core (and hence deterioration or destruction of the relay when subjected to intense vibration), and permits the magnet coil (bobbin and winding) to be integrated into a unitary mass with the core while at the same time permits the electromagnet structure to be strongly supported by the pole pieces alone, thus eliminating the added weight of the prior-art coilsupporting flanges. The rectangular poles and the cylindrical body of the core have their axes in a single plane, which simplifies manufacture of the core and makes it structurally stronger than a core with offset poles, and as Well greatly simplifies molding-on of the bobbin and winding-on of the coil. The single-plane unitary core used in the present invention requires that the arms of the armature be offset from the plane of the core, but, as mentioned, that provides for adequate space for an armature spring and for better placement of the contact actuator presently described. By making the armature of a single unitary piece, the inefficiency and lack of uniformity among armatures, and weakness and greater cost of a fusion-united two-piece armature are avoided.

For the purpose of operating switch means by the armature, there is fusion-united to one limb of the armature an actuator device 28 that comprises a resilient rod 28a carrying an 'insulative knob or bead 28b at its lower end. The bead is formed in situ on the rod, hence is rigidly secured to the rod, and is disposed in position to engage and flex the flexible contact device 16a away from contact member 166 and into contact with contact member 16d when the armature is rotated incident to energization of the magnet. The rod 23a of the actuator device is, while resilient, stiif and sutficiently strong to flex contact device tea as noted. Since in the normal rest -ber 16d and into contact with member Zine.

position of the armature 22, the bead 28b is removed from the flexible contact device 16a, the electromagnet in the initial stages of rotating the armature has only the light load presented by friction and spring 26 to overcome. Hence uponenergization the magnet may quickly set the armature into rotation; and as the air-gap between the armature and poles Zlim, an is reduced and the magnetomotive effort rapidly increases, the bead 23b engages contact device 16a and surely and readily moves the latter away from contact member 16a and into engagement with contact member 16d. Upon subsequent de-energization of the magnet, spring as returns the armature to rest position, permitting the flexible contact device 1611 to move by elastic action away from mem- Thus as the armature is moved by'the magnet, a circuit connecting terminals 16a and 162 is opened and a circuit connecting terminals 16a and 16d is closed. Similarly, the opposite action ensues when the magnet is tie-energized. Thus the switching functions of the switch are performed incident to connection of a source of electric power to terminals 16b and 160 to energize the electromagnet, and disconnection of the power to permit de-energization of the magnet.

Preferably, but not necessarily, a cover or jacket 2%: of polyiluorocarbon resin tape, such as one of the commercially-available pressure-sensitive adhesive varieties, is applied around the electromagnet coil prior to uniting the magnet poles to the pedestal.

Subsequent to physical assembly of the described operating components, the compressive force exerted on the armature by the spring 26 may be adjusted by slight compressive or expansive deformation of the spring,

tweezers or other suitable tool being used for the opera tion; or, alternatively, any other suitable mode of adjusting or providing proper spring tension may be used. .Also, the spacing of the contacts, and the bead on rod 28a,

are adjusted, and at that time the switch device may be tested for satisfactory operation. Following the preceding operations, the cap or cover 12 is placed over the operating parts and soldered or fusion-united with the rim 14b of the header 14, providing an hermetic seal around that periphery. Thereafter the interior of the housing isexhausted and filled with an inert gas such as -a mixture of helium and dry nitrogen, the gas being introduced through an aperture 12a (FIG. 1) provided in the can or cover; and the aperture thereupon sealed off as by means of solder.

As is made evident in F TGS 4 and 10, the armature is formed of a single piece of ferromagnetic material and ator, by removal of material at an appropriate one of the lower outer corners of the armature. Thus the armature is made insensitive to acceleration in any direction perpendicular to its axis of rotation. And since the armature is restricted in the direction of the axis, the switch 'is substantially entirely free of adverse effects induced or caused by acceleration. Also, the magnet core (FIG.

7 1:1) is formed of U shape and as an integral piece of ferromagnetic material. Thus the core and armature provide a magnetic circuit of high efficiency. All of the materials used in header, pedestal, electromagnet, con- 'tacts, armatures, etc., are such as to be not adversely affected by heat at high ambient-temperatures. Since all of the major non-moving components of the switch are integraily fusion-united into :a single structure, the

components retain their respectivepositions and thus I damage or disintegration of the switch due to vibration and/or shock is substantially entirely obviated and the initial adjustmentspof the components last for the life of the device. Also, much-desired extreme uniformity among a group of the relays is attained.

The preceding description makes evident the fact that the aforementioned objects of the invention have been fully attained. It is evident that in the light of that description, changes of form or other changes in the structure will he suggested to those skilled in the art. Ac

cordingly we do not wish to be limited to the exact details of the exemplary device disclosed, but we claim:

1. A very small electromagnetic switch comprising:

first means, comprising housing means including a base means;

second means, comprising supporting means in the formof a rigid table-like pedestal means having more than'two legs each of said legs being fusionunited at its 10lW61 end to said base means to form therewith an integral structure;

third means, comprising an electromagent means comprising a one-piece U-shaped magnetic core having first and second dependent legs, said electromagnet means comprising a molded bobbin integrally united with said core and a magnet winding on said bobbin,

and the first and second legs of said core being fusion-united adjacent their ends with said pedestal to form an integral structure therewith, and said third means comprising an armature pivot fixed to said pedestal means, and a movable armature means pivotally mounted on said pivot and constructed and arranged for cooperative magnetic interaction with said first and second legs of said magnetic core;

and fourth means, comprising terminal means and fixed and movable contact means, constructed and arranged to provide an electrical circuit through said winding, and said movable contact means being operable'by said armature means incident to energization of said electromagnet means. for closing a second electrical circuit including said fixed and movable contact means; whereby under the influence of extremely high vibratory accelerations there are no changes in the magnetic-circuit of said core and no changes in the electromagnetic characteristics of the combination comprising said core and the bobbin and coil thereon.

2. An electromagnetic switch device comprising:

first means, including a header means having opposite sides and including an insulative portion and feedthrough terminal means sealed therein and encircled by a metallic rim portion;-

second means, including a one piece table-like pedestal means having a substantially flat top and a plurality of limbs rigidly united to said metallic rim portion at respective pairs of spaced-apart locations on each of said sides to rigidly integrate the pedestal means and the header means;

third means, including electromagnet means comprising essentially an integral one-piece U-shaped magnetic core and an insulative coil bobbin thereon integrally united therewith and an energizing coil on the bobbin, the ends of said core being fusion united to said pedestal means at spaced-apart locations to thereby rigidly support said electromagnet means on said frame means to obviate any relative motion therebetween; and

fourth means, comprising electrical connections from said coil to certain ones of said terminals, and comprising means including electric-switch means operable by said electromagnet means incident to energization and de-energization'of thelatter means.

3. In a very small electromagnetic switch device, the

combination comprising: 7

first means, comprising a rigid non-magnetic tablelike frame comprising a platform-like top and pairs of depending legs; I

second means, comprising an electromagnet comprising a one-piece U-shapedmagnetic core'integra-lly united at its ends to said frame, a coil bobbin rigidly integrated with said core and a magnet coil on the bobbin, said core having a body portion and depending legs and the axis of the legs and the body being co-plan-ar;

third means, comprising a pivotal one-piece armature and pivot means therefor on said frame, said pivot means having its axis substantially in the plane of the axes of said core and said armature having ends offset on respective sides of a plane through the axis of its pivot, and said third means comprising spring means effective to urge the armature in one direction and said eleotromagnet being constructed and arranged to urge said armature in .a second direction; and

fourth means, comprising switch means constructed and arranged to be operated by said armature.

4. In a very small electromagnetic switch device the combination comprising:

a one-piece U-shaped ferromagnetic core;

a poly fluorocarbon coil-bobbin on and integrally united with said core and provided with passage means for electric-conductor means;

coil means wound on said bobbin and including insulated electric-conductor means disposed in said passage means, said core and said coil means forming an electromagnet;

integral non-magnetic table-like frame means having a a plurality of legs and a top portion to which said core is fusion-united for support of said core and said coil means by said frame means; and

means including electric-switch means constructed and arranged for operation by the elect-romagnet comprising said core and said coil means; whereby the means forming said electromagnet remain stationary each with respect to the others under extremely severe vibration and whereby the electromagnet remains stationary with respect to said frame means during such vibration.

5. In a very small electromagnetically operated switch device, the sub-assembly comprising:

a unitary integral table-like frame having a substantially-unobstructed substantially-flat upper surface and a plurality of depending legs and first and second outwardly extending limbs;

a rotary armature means and a pivot therefor secured to said frame below said surface, said armature means being disposed for cooperation with a magnet core;

an electromagnet comprising a U-shaped one-piece core and an insulative bobbin integrally united there- 10 with the ends of said core being fusion-united with respective ones of said limbs of said frame to form a unitary structure therewith; said electromagnet including a magnet coil on said bobbin encircling said core. 6. For a very small electromagnetically-operated switch, the sub-assembly comprising:

first means, comprising an integral table-like frame means having depending legs and a substantiallyfiat substantially-unobstructed upper surface and comprising laterally extending limbs at opposite lateral extremities of the frame means and including a laterally extending stop means disposed opposite one of said limbs;

second means, comprising a pivot-pin means secured to said frame means and disposed between said laterally extending limbs and below said upper surface;

third means, comprising a balanced elongate rotary ferromagnetic armature rotatably mounted on said pivot-pin means and having first and second ends disposed adjacent respective ones of said limbs and one end thereof disposed between said stop means and one of said Limbs;

and fourth means, comprising :an electromagnet comprising .a U-shaped one piece ferromagnetic core and an insulative bobbin integrally united to said core to provide an integral structure therewith, and an energizing coil on said bobbin, the ends of said core being fusion-united with respective ones of said laterally extending limbs of said frame means to provide a rigid integral structure therewith, and the ends of said core being positioned for magnetic cooperation with respective ends of said armature.

References Cited by the Examiner UNITED STATES PATENTS 2,905,913 9/59 Leigh 336--83 2,923,794 2/60 Keeran 3l7-197 2,93 1, 872 4/60 Sprando 20087 2,949,591 8/60 Oraige 336-433 2,951,134 8/60 Lazich 20087 2,960,583 11/60 Fisher et al. 20087 3,005,071 10/61 Brunicardi 20087 3,118,033 1/64 Somers et al. 200-104 3,147,349 9/64 Welch et al. 200-87 BERNARD A. GILHEANY, Primary Examiner.

MAX L. LEVY, ROBERT K. SCHAEFER, Examiners. 

1. A VERY SMALL ELECTROMAGNETIC SWITCH COMPRISING: FIRST MEANS, COMPRISING HOUSING MEANS INCLUDING A BASE MEANS; SECOND MEANS, COMPRISING SUPPORT MEANS IN THE FORM OF A RIGID TABLE-LIKE PEDESTAL MEANS HAVING MORE THAN TWO LEGS EACH OF SAID LEGS BEING FUSIONUNITED AT ITS LOWER END TO SAID BASE MEANS TO FORM THEREWITH AN INTEGRAL STRUCTURE; THIRD MEANS, COMPRISING AN ELECTROMAGNET MEANS COMPRISING A ONE-PIECE U-SHAPED MAGNETIC CORE HAVING FIRST AND SECOND DEPENDENT LEGS, SAID ELECTROMAGNET MEANS COMPRISING A MOLDED BOBBIN INTEGRALLY UNITED WITH SAID CORE AND A MAGNET WINDING ON SAID BOBBIN, AND THE FIRST AND SECOND LEGS OF SAID CORE BEING FUSION-UNITED ADJACENT THEIR ENDS WITH SAID PEDESTAL TO FORM AN INTEGRAL STRUCTURE THEREWITH, AND SAID THIRD MEANS COMPRISING AN ARMATURE PIVOT FIXED TO SAID PEDESTAL MEANS, AND A MOVABLE ARMATURE MEANS PIVOTALLY MOUNTED ON SAID PIVOT AND CONSTRUCTED AND ARRANGED FOR COOPERATIVE MAGNETIC INTERACTION WITH SAID FIRST AND SECOND LEGS OF SAID MAGNETIC CORE; AND FOURTH MEANS, COMPRISING TERMINAL MEANS AND FIXED AND MOVABLE CONTACT MEANS, CONSTRUCTED AND ARRANGED TO PROVIDE AN ELECTRICAL CIRCUIT THROUGH SAID WINDING, AND SAID MOVABLE CONTACT MEANS BEING OPERABLE BY SAID ARMATURE MEANS INCIDENT TO ENERGIZATION OF SAID ELECTROMAGNET MEANS FOR CLOSING A SECOND ELECTRICAL CIRCUIT INCLUDING SAID FIXED AND MOVABLE CONTACT MEANS; WHEREBY UNDER THE INFLUENCE OF EXTREMELY HIGH VIBRATORY ACCELERATIONS THERE ARE NO CHANGES IN THE MAGNETIC-CIRCUIT OF SAID CORE AND NO CHANGES IN THE ELECTROMAGNETIC CHARACTERISTICS OF THE COMBINATION COMPRISING SAID CORE AND THE BOBBIN AND COIL THEREIN. 